Impregnation of paper or other materials, more especially for the protection of vegetable and animal goods during storage



Patented Jan. 2, 1940 Arthur Ryner, London, England, assignor to Preservators Limited, London, England, a company of Great Britain No Drawing. Application September 29, 1937,

Serial No. 166,457. In Great Britain October 11 Claims.

This invention relates to the protection of vegetable and animal goods during storage.

It has already been proposed to protect such goods by imparting a controlled and limited albases adapted to give off an alkaline gas will first be described.

In view of the fact that paper is subject to deterioration, especially if it be thin, when soaked kalinity to the atmospheric air surrounding the for a lon pe in a solution and since it is goods during storage. The pH value of the air portant that the impregnating or coating subis preferably maintained at about 7.5 and this is ces fi mly adhere 0 the P and p u achieved by diffusing a gaseous alkaline subthe maximum loading t it is preferred to stance into the atmosphere, as for example, by i p e nate th p p y Passing it through a 11013 burning combustible porous bodies which have saturated solution of the desired substance. The previously been impregnated with a. substanc solution is maintained at saturation point and which yields a gaseous alkali, by allowing gaseous the pref d temperature is about It is monia to escape from a bottle of liquefied mfound that the hot solution penetrates in to the monla, by spraying or evaporating amines or paper in a relatively short time and that the lutions thereof into the atmosphere or by placing tte p y dries, after leaving the Solution, in the storage chamber heaps of a subst while being traversed through the air and/or Such as ammonium carbonate, which gives off subjected to the drying effect of a current of air.

a gaseous alkali under normal conditions. He 0 t impregnated p p should he The means which have been proposed for m. avoided as much as possible since it causes rapid parting the desired alkalinity to the air, while evolution of the alkaline gas.

suitable for use on a large scale, ar h t t When it is desired to repel flies and insects small tradesmen and individual householders are m the foodstufis being preserved he p p r practically precluded from availing themselves of the like may be impregnated or coated with amthe use of the process for protecting small stores monhlm formate ammonium lactate One of vegetable and animal goods, side of the paper or the like may be coated with An important object of the invention is to pro- One of the substances yielding an alkaline gas vide improved means whereby users on b th and the other side may be coated with formic large and small scale may conveniently and safeacid lactic applied in Solution. Ag ly employ the process referred to above, such the foodstuff may be Wrapped 3 enclosed means being supplied ready for use and needing in an ihhel Covering impregnated with a no preparation by the user while not involving the Stance yielding an alkaline gas and an Outer ri k of fire or contamination of t goods t be ering impregnated with a substance which repels preserved, flies and insects. In some cases both classes of A further object of the invention is to provide substances may he applied to a common base, means which shall be such as to repel flies and Paper, over adjacent areasinsects from the neighborhood of the stored goods In Order that the emciehey 0f the preservlhg and yet another object is the provision of an im- Process may be checked conveniently and 935113 proved method of producing the means according there may be provlded, either on a separate card to the invention or the like or on an edge of' the paper which According to the invention there is provided has not been impregnated with t he Substance 40 a paper or other carrier or base impregnated or referred to above, a series of sensitive indicattolrs coated with a substance adapted to evolve an alf q to change F m dependence upon kaline gas under the conditions of use the imaumty of the am example three.s.ma1

. pieces of paper (or three areas of the margin of pregnating or coating substance being such that the wrapping paper prepared as above described) the impregnated or coated base or carrier is normay be impregnated respectively with the mally quiescent and only evolves the alkaline gas lowing solutions. when subjected to the action of carbon dioxide (a) A @0470 solution f brom cresol purple in evolved by the stored goods. iso-propyl alcohol,

Other features of the invention will appear (b A (102 solution of phen01 red in from the following description of some examples propyl alcohol, and of the way in which it may be carried into effect (c) A 0.04% solution of brom-thymol-blue in and are detailed in the claims appended to this iso-propyl alcohol. specification. Initially these impregnated pieces or areas of The production of paper or like carriers or paper are-of substantially the same yellowishbrown colouration but as soon as they are placed in an alkaline atmosphere the paper impregnated with solution (a) becomes coloured a deep blueviolet. If the pH value of the atmosphere is approximately 7.5 the paper impregnated with solution (b) becomes coloured a rose-pink but should this value be greatly exceeded the paper impregnated with solution (c) becomes coloured a pale almond-green. It will be understood that these colour changes all occur to varying degrees for degrees of alkalinity of the atmosphere varying from zero upwards and that reference to a suitably calibrated colour chart permits of a close approximation to the degree of alkalinity of the atmosphere prevailing at any instant.

Such a chart could be printed on the impregnated paper or the like or supplied therewith and directions for use and other matter may also be printed on or otherwise applied to the packing or wrapping material according to the invention.

According to the invention, the carbon dioxide which all vegetable and animal goods evolve during storage is utilised as a controlling factor for the dissemination of the alkaline gas so as to maintain the pH value of the air surrounding the goods substantially constant at '7 or thereabouts.

The means provided for this purpose. therefore, is such that evolution or generation of the gas imparting alkalinity to the atmosphere only takes place in the presence of carbon dioxide and proportionately to the concentration thereof.

To this end, the paper, packing material or another suitable base is impregnated or coated with a' substance adapted to be decomposed by, or to react chemically with, carbon dioxide with the simultaneous liberation of gaseous ammonia. Examples of such substances are the known complex compounds of metals with ammonia. and acid radicals, such as those believed to have the formulae (CH(NH3)4)CO3 and (Ca(NHa)4)COs. These compounds evolve ammonia in the presence of carbon dioxide, presumably with the formation of other complex compounds in which one or more of the NHL; groups has or have been substituted by a C02 group.

It is preferred to form the complex compounds in situ in the pores or on the fibres of the paper or the like, more especially when they are insoluble or only slightly soluble, but when. the complex compounds are soluble they may be applied in solution by any suitable impregnating or coating process.

The complex compounds may be produced by any of the usual methods which form no part of the present invention.

Paper or the like which has been impregnated or coated with a substance of the character re ferred to may be stored for long periods w thout deterioration yet is so sensitive to the presence of CO2 that if breathed upon from a distance of about two feet sufficient ammonia gas is liberated for its characteristic odour to be easily recognised. The paper or the like may be wrapped around the goods to be protected. used as a lining to crates, baskets or boxes for the said goods or employed in other ways.

It is desirable in many instances to protect the paper or the like from the action of damp or moisture and for this purpose there may be applied an outer covering or coating of a waterproof material, e. g.. a waterproof varnish, a cellulose lacquer, a cellulose acetate film or the like. In order that the dissemination of the alkaline gas may still occur in the presence of 00:, however, the paper or the like is perforated subsequent to the waterproofing treatment so that the impregnated material will be freely exposed at the walls of the perforations.

The perforations also serve to permit of ventilation of the goods being protected since they allow of the circulation of air. By suitably proportioning the sizes of the perforations with re-- lation to the thickness of the paper or the like there may be obtained a degree of automatic regulation of the ventilation.

Furthermore the area of paper or the like available for the dissemination of the alkaline gas may be exactly determined, and may even be increased to a value exceeding the combined area of the outer surfaces of the paper or the like, by suitably selecting the size and number of the perforations. For example, a sheet of paper, which has been impregnated and waterproofed in the manner described, may be formed with a large number ofclosely spaced small holes of a diameter approximating in length to the thickness of the paper. The total area of the walls of the holes then amounts to approximately 50% more than the total area of the two surfaces of the sheet. At the same time the perforations are so small that moisture cannot penetrate them.

In order to increase the eflective area for the dissemination of the gas, or to concentrate the desired effect at a predetermined location, the paper or other carrier or base may be corrugated,

creped, crinkled or folded either over its entire expanse or over a part thereof, as the case may be What I claim is:

1. Wrapping, packing and like materials for use in association with vegetable and animal goods to protect them during storage comprising a carrier material carrying a complex compound of a metal with ammonia and an acid radical which evolves ammonia when subjected to the action of carbon dioxide.

2. For use in association with vegetable and animal goods to protect them during storage, a carrier material impregnated, at least on one side, with a complex compound of a metal with ammonia and an acid radical which evolves ammonia when subjected to the action of carbon dioxide.

3. A carrier material for association with vegetable and animal goods during storage thereof consisting of a packing material which carries a complex compound of a metal with ammonia and an acid radical, the said compound evolving ammonia under the action of carbon dioxide, and which is provided with a waterproof coating to protect it against the action of damp.

4. A carrier material as claimed in claim 3, formed with perforations to ensure the ventilation of the goods.

5. A carrier material as claimed in claim 1,- formed with folds and creping to increase its effectiv'e area.

6. A carrier material as claimed in claim 1, which includes a substance such as lactic acid which is shunned by flies and insects.

7. A wrapper for use with vegetable and animal goods during the storage thereof comprising a packing material carrying a complex metalammonia compound which liberates ammonia under the action of carbon dioxide.

8. A wrapping paper for vegetable and animal agsmee 3 goods which is impregnated. with a complex}- formed with folds and creping to increase its at metal-ammonia compqund adapted to evolve amfective area. mania. under the action 01 carbon dioxide. I 11. A carrier material as claimed in claim 3, 9. A wrapper as claimed in claim 7,-formed with embodying as the ammonia evolving compound a 5 perforations to ensure ventilation of the goods. complex copper-ammonium salt.

10. A wrapping paper as claimed in claim.8, ARTHUR RYNER. 

